A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

A spark plug includes a central electrode member and an outer electrode member. The central electrode member includes a central base and a plurality of electrode prongs extending in an axial direction from the central base. The outer electrode member surrounds the central electrode member. The outer electrode member includes a wall that is radially spaced from the plurality of electrode prongs to allow a series of electric arcs to form between the wall and the plurality of electrode prongs. The outer electrode member and the central electrode member are sized and positioned relative to one another such that a first rate of wear of the outer electrode member, along a longitudinal axis of the spark plug, is substantially equal to a second rate of wear of the central electrode member along the longitudinal axis.

At least one of a center electrode and a ground electrode of a spark plug includes an electrode body, an electrode tip, and a welded portion formed between the electrode body and the electrode tip. The electrode tip includes a cover layer that covers at least a side surface of a tip body, and the cover layer is formed of IrAl. On a section formed by cutting the electrode tip near a boundary with the welded portion, an area of the tip body is represented by Sa. An area of a projection on the section of a non-contact portion of an opposite surface of the tip body not in contact with the welded portion is represented by Sb. In this case, Sa−Sb corresponds to 35% or more of Sa.

At least one of a center electrode and a ground electrode of a spark plug includes an electrode body, an electrode tip, and a welded portion formed between the electrode body and the electrode tip. The electrode tip includes a cover layer that covers at least a side surface of a tip body, and the cover layer is formed of IrAl. On a section formed by cutting the electrode tip near a boundary with the welded portion, an area of the tip body is represented by Sa. An area of a projection on the section of a non-contact portion of an opposite surface of the tip body not in contact with the welded portion is represented by Sb. In this case, Sa−Sb corresponds to 35% or more of Sa.

A spark plug, including a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated relative to one another in such a way that the ground electrode and the center electrode form a spark gap, and the ground electrode including a core and a sheath surrounding the core, the core being made of a material which has a higher thermal conductivity than the material of the sheath, and a cross sectional area of the ground electrode being not greater than 2.76 mm.sup.2, the sheath having a wall thickness c of not greater than 0.4 mm in a first region of the ground electrode.

A spark plug, including a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated relative to one another in such a way that the ground electrode and the center electrode form a spark gap, and the ground electrode including a core and a sheath surrounding the core, the core being made of a material which has a higher thermal conductivity than the material of the sheath, and a cross sectional area of the ground electrode being not greater than 2.76 mm.sup.2, the sheath having a wall thickness c of not greater than 0.4 mm in a first region of the ground electrode.

A pre-chamber spark plug for igniting a fuel-air mixture in an internal combustion engine, in particular a gasoline engine, comprises a spark plug body (1) having a pre-chamber housing (2) and a cap (4) which at least partially closes the pre-chamber (3), and further comprises a ground electrode (11) in the spark plug body (1) as well as a central electrode (7) which protrudes into the pre-chamber (3); the ground electrode (11) has an annular shape and, on the inner surface thereof, includes at least one ignition area (17) designed as a cam (16) as well as a radially inward extending protrusion (18) as a baffle (19).

An electrode tip assembly for a spark plug includes an electrode tip that is formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique, after which the electrode base is welded to an electrode body. The electrode base includes a welding side and an additive manufacturing side, and the electrode tip includes a plurality of laser deposition layers built on the additive manufacturing side of the electrode base.

An electrode tip assembly for a spark plug includes an electrode tip that is formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique, after which the electrode base is welded to an electrode body. The electrode base includes a welding side and an additive manufacturing side, and the electrode tip includes a plurality of laser deposition layers built on the additive manufacturing side of the electrode base.

In a cross section including a central axis, a value L/D obtained by dividing an axial length L of an overlap portion where a metal contact surface located on a metal shell and on which a packing is in contact with the metal shell overlaps a projection plane located on the metal shell and on which a contact surface located on an insulator and on which the packing is in contact with the insulator is projected in a direction orthogonal to the central axis by a difference D between a radius of an outer circumference of a tube portion at a connection position to a step portion and a radius of an outer circumference of a leg portion at a connection position to the step portion is 1.2 or more. This ensures the force of constraint in the radial direction provided by the packing on the insulator.